Compressor

ABSTRACT

Provided is a compressor operable with suppressing moisture adhesion to an impeller. This compressor includes; a tubular casing forming an annular space; a motor within the casing&#39;s annular space with having a gap between the casing and the motor; a rotary shaft extending downstream from the motor, for outputting rotational driving force of the motor; an impeller affixed to the rotary shaft downstream from the motor, and that compresses an operating fluid; and first guide blades in the gap and configured so as to impart a swirl component to operating fluid passing through the gap and moving toward the impeller due to the rotation of the impeller. A first moisture accommodation hole and a first discharge port, which open toward the portion of the annular space located between the impeller and the first guide blades and are for discharging moisture in the operating fluid, are formed in the casing.

TECHNICAL FIELD

The present invention relates to a compressor, and particularly to a compressor used in a gas field which produces natural gas.

BACKGROUND ART

In recent years, gas fields to be developed have been shifting from conventional type gas fields to non-conventional type gas fields with increasing demands for fossil fuels and advancement of mining technologies. This shift of gas field development produces the necessity of placing a compressor in a harsh environment such as an environment immediately below a gas field. To cope with the environment immediately below a gas field, there has been proposed a method which places a compressor inside a gas well several thousands of meters underground, compresses gas at the bottom of the well by using the compressor, and supplies the compressed gas to the ground. Research and development of a compressor suitable for this method (a downhole-type compressor) have been in progress.

A gas field has a high underground pressure in an initial stage of development, while the pressure inside the field drops with advancement of gas extraction. During a period of a high underground pressure of a gas field, natural gas naturally flows and reaches the ground. When the pressure drops to a limit pressure or lower, however, a sufficient natural flow of the gas cannot be achieved. Accordingly, a gas well after a pressure drop has been treated as a dry-up well.

Nevertheless, a considerable quantity of natural gas remains inside a gas field even after a drop of underground pressure to a level insufficient for natural flow of the gas. The production ability of the gas field is considered to recover even in this condition when a pressure immediately below the gas field is boosted by using a downhole compressor. The downhole compressor described above is placed at the bottom of the gas field or immediately below the gas field, and therefore operates in an extremely harsh operating environment.

A compressor used in a gas field which produces natural gas is generally characterized by an operating environment of the compressor, i.e., such an operating environment in which not only natural gas, but also water and liquid containing light liquid hydrocarbon called condensate are mixed into working fluid of the compressor. Particularly an environment immediately below a gas field contains liquid at an extremely high rate. Liquid having entered the inside of the compressor in this environment is considered to reduce efficiency as a result of collision with an impeller, reduce an operating range or generate instable fluid force as a result of closure of a channel caused by fouling, and reduce the thickness of the impeller as a result of erosion. Accordingly, development of a technology for a compressor used in a gas field which produces natural gas is required to allow the compressor to operate without lowering performance even in the operating environment causing mixture of liquid.

Patent Literature 1 discloses a structure which removes droplets mixed into an impeller of a compressor.

CITATION LIST Patent Literature PATENT LITERATURE 1: JP-A-2013-508618 SUMMARY OF INVENTION Technical Problem

By the compressor disclosed in Patent Literature 1, however, droplets mixed into the impeller cannot be sufficiently removed.

Accordingly, an object of the present invention is to provide a compressor capable of suppressing adhesion of liquid to an impeller without dropping efficiency of the impeller and reducing an operating range during operation.

Solution to Problem

For achieving the above object, a compressor according to the present invention includes: a casing that has a columnar shape and forms a space; a motor provided within the space of the casing with a clearance left between the casing and the motor, a rotation shaft that extends downstream from the motor, and is configured to output rotational driving force of the motor; an impeller fixed to the rotation shaft on a downstream side with respect to the motor, and configured to compress working fluid; and a first guide vane provided in the clearance, and configured to give a swirl component to working fluid that passes through the clearance and approaches the impeller in accordance with rotation of the impeller. The casing includes a first drain hole opened to a portion between the impeller and the first guide vane in the space, liquid contained in the working fluid being discharged through the first drain hole.

Advantageous Effects of Invention

According to the present invention, there can be provided a compressor capable of suppressing adhesion of liquid to an impeller without dropping efficiency of the impeller and reducing an operating range during operation.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a cross-sectional view of a compressor according to a first embodiment of the present invention;

FIG. 2 shows an explanatory view of first guide vanes;

FIG. 3 shows a cross-sectional view of a conventional compressor;

FIG. 4 shows a cross-sectional view of a compressor according to a second embodiment of the present invention;

FIG. 5 shows a cross-sectional view of a compressor according to a third embodiment of the present invention; and

FIG. 6 shows a cross-sectional view of a compressor according to a fourth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

A compressor 1 according to a first embodiment of the present invention is hereinafter described with reference to the drawings. The compressor 1 according to the present embodiment, which is called downhole compressor, is a turbo compressor used within a gas well of a gas field which produces natural gas, for example. Not only natural gas, but also water and liquid containing light liquid hydrocarbon called condensate are mixed into working fluid.

FIG. 1 is a cross-sectional view illustrating only a left half of a main part of the compressor 1 according to the first embodiment.

As illustrated in FIG. 1, the compressor 1 includes a casing 16, a motor 2, a rotation shaft 11, an impeller 10 and first guide vanes 15.

The casing 16 has a cylindrical shape with a coaxial penetration space 16 a, and includes a motor housing portion 16B an intermediate portion 16C, and a discharge portion 16D. The motor housing portion 16B houses the motor 2, and includes an inner circumferential face 16 e. The intermediate portion 16C is positioned on the downstream side with respect to the motor housing portion 16B, and has an inclined face 16 e which extends downstream while inclined toward the rotation shaft 11. Accordingly, the inclined face 16 e of the intermediate portion 16C reduces the diameter of the penetration space 16 a.

The intermediate portion 16C further includes a first liquid storage hole 13 and a first drain port 14. The first liquid storage hole 13 is opened to a portion of the penetration space 16 a between the impeller 10 and the first guide vane 15, and configured to store liquid. The first drain port 14 connects the first liquid storage hole 13 and the outside of the casing 16 such that the first liquid storage hole 13 and the outside can communicate with each other. Liquid having entered the first liquid storage hole 13 passes through the first drain port 14, and goes out of the casing 16 for discharge. The first liquid storage hole 13 and the first drain port 14 correspond to a first drain port.

The discharge portion 16D is located on the downstream side with respect to the intermediate portion 16C, and includes both an inlet face 16 f extending downstream from the inclined face 16 e and a discharge face 16 g. The discharge face 16 g and an impeller body 10A described below constitute a discharge path 12 b. The inlet diameter of an inlet port 16 h for gas defined by the inlet face 16 f is smaller than the outside diameter of the motor 2.

The motor 2 is constituted by a motor casing, a stator and a rotor. A cylindrical clearance 16 i is formed between an outer circumferential face 2A of the motor 2 and an inner circumferential face 16 e of the motor housing portion 16B. As illustrated in FIG. 2, a plurality of the first guide vanes 15 are provided on the outer circumferential face 2A of the motor 2 and arranged in the circumferential direction. Accordingly, a plurality of first guide vanes 15 is located in the clearance 16 i. Each of the first guide vanes 15 is curved, and configured to give a swirl component to working fluid passing through the clearance 16 i.

The rotation shaft 11 extending in the upstream-downstream fluid flowing direction is fixed to the rotor of the motor 2 and configured to rotate together with the rotor.

The impeller 10 is a centrifugal fan, and is fixed to the rotation shaft 11 in the vicinity of a position corresponding to the discharge portion 16D. The impeller 10 includes the impeller body 10A, and a plurality of vanes 12 provided at equal intervals in the circumferential direction. The impeller body 10A and the discharge portion 16D constitute the discharge path 12 b.

In such a configured compressor 1, if the motor 2 is driven, a plurality of impellers 10 rotates as the rotor rotates. Due to rotation of the impellers 10, the working fluid containing a mixture of gas and liquid flows into the casing 16 through a port for suction, not-shown. After the speed and pressure of the working fluid are raised within the casing 16, the working fluid passes through the clearance 16 i, as indicated by an arrow A1. The working fluid is given a swirl component while passing through the clearance 16 i and consequently passing through the plurality of first guide vanes 15. As a result, the working fluid within the casing 16 swirls as indicated by an arrows group A2.

Centrifugal force generated by these swirls separates the working fluid into gas and liquid. In this case, the liquid having higher density than that of the gas shifts outward, and flows into the first liquid storage hole 13 when the working fluid passes through the intermediate portion 16C. The liquid having entered the first liquid storage hole 13 goes out of the casing 16 for discharge through the first drain port 14, as indicated by an arrow A3.

On the other hand, the working fluid having passed through the inclined face 16 e passes the inlet port 16 h. Thereafter, the working fluid is compressed by the impeller 10, and discharged via the discharge path 12 b, as indicated by the arrow A4.

According to the compressor 1 described above, the first guide vanes 15 provided in the clearance 16 i are configured to give a swirl component to the working fluid which passes through the clearance 16 i and flows toward the impeller 10 in accordance with rotation of the impeller 10. Moreover, the first liquid storage hole 13 and the first drain port 14 formed in the casing 16 are opened to a portion of the penetration space 16 a between the impeller 10 and the first guide vanes 15 to discharge liquid contained in working fluid.

According to such configured arrangement, the swirl component having been given to the working fluid from the first guide vanes 15 separates the working fluid into gas and liquid. The liquid thus separated enters the first liquid storage hole 13, and goes out of the casing 16 from the first drain port 14. This configuration efficiently removes liquid contained in the working fluid, and therefore suppresses adhesion of the liquid to the vanes 12 of the impeller 10, and an efficiency reduction due to an undesirable increase of shaft power of the impeller 10. Moreover, suppression of adhesion of liquid to the vanes 12 and the discharge face 16 g of the discharge portion 16D is also achievable. This configuration therefore suppresses narrowing of a channel width of the working fluid, thereby allowing the compressor 1 to operate without reducing the operating range of the impeller 10. Furthermore, this configuration eliminates the necessity of a supplementary device provided to capture liquid, thereby achieving size reduction of the compressor 1.

According to a conventional compressor 3 illustrated in FIG. 3, however, liquid contained in working fluid adheres to the vanes 12 of the impeller 10 and the discharge face 16 g of the casing 16. As a result, shaft power of the impeller 10 increases, while efficiency of the compressor 3 drops. Moreover, droplets having adhered to the vanes 12 and the discharge face 16 g narrow a channel width of working fluid, causing reduction of the operating range and generation of unstable fluid force, and reducing the thickness of the vanes 12 by erosion. However, the compressor 1 according to the present embodiment can solve these problems arising from the conventional compressor 3.

Furthermore, the outside diameter of the motor 2 is larger than that of the inlet diameter of the inlet port 16 h. In this case, working fluid passes through the outer circumference of the motor 2 and reaches the impeller 10. Accordingly, the motor 2 can be cooled by the working fluid and can achieve efficient rotation.

In addition, the first liquid storage hole 13 and the first drain port 14 constitute the first drain hole. In this case, liquid is temporarily stored in the first liquid storage hole 13, and goes out of the casing 16 through the first drain port 14. Accordingly, efficient discharge of liquid contained in working fluid is achievable.

A compressor 21 according to a second embodiment of the present invention is hereinafter described with reference to FIG. 4. Constituent elements identical to the corresponding constituent elements of the compressor 1 according to the first embodiment are given identical reference numbers, and are not repeatedly described herein. Accordingly, only different configurations are touched upon in the following description.

FIG. 4 is a cross-sectional view illustrating only a left half of a main part of the compressor 21 according to the second embodiment.

As illustrated in FIG. 4, the intermediate portion 16C of the compressor 21 according to the present embodiment includes a second liquid storage hole 17 and a second drain port 18. The second liquid storage hole 17 is opened to the penetration space 16 a at a position on the downstream side with respect to the position of the first liquid storage hole 13 in the flow of working fluid. The second liquid storage hole 17 is configured to store liquid. The second drain port 18 connects the second liquid storage hole 17 and the outside of the casing 16 such that the second liquid storage hole 17 and the outside can communicate with each other. Liquid having entered the second liquid storage hole 17 passes through the second drain port 18, and goes out of the casing 16 for discharge. The second liquid storage hole 17 and the second drain port 18 correspond to a second drain hole.

According to the present embodiment, working fluid having passed through the first liquid storage hole 13 swirls as indicated by arrows A5. Liquid contained in the working fluid enters the second liquid storage hole 17. The liquid having entered the second liquid storage hole 17 goes out of the casing 16 for discharge through the second drain port 18 as indicated by an arrow A6.

According to the compressor 21 of the present embodiment described above, liquid contained in working fluid also goes out of the casing 16 via the second liquid storage hole 17 and the second drain port 18. This configuration therefore further suppresses adhesion of liquid to the vanes 12 of the impeller 10, thereby suppressing an efficiency drop caused by a rise of shaft power of the impeller 10. Moreover, this configuration further suppresses adhesion of liquid to the vanes 12 and the discharge face 16 g of the discharge portion 16D, thereby suppressing narrowing of a channel width of working fluid, and allowing the compressor 21 to operate without reducing the operating range of the impeller 10.

Furthermore, the inclined face 16 e reduces the diameter of the penetration space 16 a. This configuration increases swirl force of working fluid, thereby promoting separation of working fluid into gas and liquid. Accordingly, efficient removal of liquid contained in working fluid, and further suppression of adhesion of liquid to the vanes 12 of the impeller 10 are achievable.

A compressor 31 according to a third embodiment of the present invention is hereinafter described with reference to FIG. 5. Constituent elements identical to the corresponding constituent elements of the compressor 1 according to the first embodiment are given identical reference numbers, and are not repeatedly described herein. Accordingly, only different configurations are touched upon in the following description.

FIG. 5 is a cross-sectional view illustrating only a left half of a main part of the compressor 31 according to the third embodiment.

As illustrated in FIG. 5, a plurality of second guide vanes 19 are provided on the casing 16 of the compressor 31 according to the present embodiment. The respective second guide vanes 19 project from the inlet face 16 f toward the rotation shaft 11 substantially at equal intervals in the circumferential direction. In addition, each of the second guide vanes 19 has a plate shape, and is disposed in parallel with the upstream-downstream direction.

According to the compressor 31 of the present embodiment configured as above, the respective second guide vanes 19 can reduce a swirl component of working fluid given from the first guide vanes 15. Accordingly, this configuration can smoothly change a flow of working fluid in the vertical direction to a flow in the horizontal direction in the impeller 10, thereby suppressing an efficiency drop of the impeller 10. Moreover, other effects similar to the effects of the compressor 1 of the first embodiment can be produced.

A compressor 41 according to a fourth embodiment of the present invention is hereinafter described with reference to FIG. 6. Constituent elements identical to the constituent elements of the compressors 1, 21, and 31 according to the first to third embodiments are given identical reference numbers, and are not repeatedly described herein. Only different configurations are touched upon in the following description.

FIG. 6 is a cross-sectional view illustrating only a left half of a main part of the compressor 41 according to the fourth embodiment.

As illustrated in FIG. 6, the compressor 41 according to the present embodiment includes not only the configuration of the compressor 1 of the first embodiment, but also the second liquid storage hole 17 and the second drain port 18 formed in the intermediate portion 16C similarly to the compressor 21 of the second embodiment, and the plurality of second guide vanes 19 formed on the casing 16 similarly to the compressor 31 of the third embodiment.

According to the compressor 41 of the present embodiment, therefore, liquid contained in working fluid can be efficiently removed via the first liquid storage hole 13 and the first drain port 14, and the second liquid storage hole 17 and the second drain port 18. Accordingly, the compressor 41 can operate without dropping efficiency of the impeller 10 and reducing the operating range.

Note that the present invention is not limited to the embodiments described above. Various additions, modifications and the like can be made by those skilled in the art within the scope of the present invention.

For example, the plurality of first guide vanes 15 provided on the outer circumferential face 2A of the motor 2 in the embodiments described above may be disposed on the inner circumferential face 16 e of the motor housing portion 16B of the casing 16. In addition, the impeller 10 constituted by a centrifugal fan in the embodiments described above may be an axial flow fan or a mixed flow fan.

REFERENCE SIGNS LIST

-   1, 21, 31, 41 Compressor -   2 Motor -   10 Impeller -   11 Rotation shaft -   12 Vane -   13 First liquid storage hole -   14 First drain port -   15 First guide vane -   16 Casing -   17 Second liquid storage hole -   18 Second drain port -   19 Second guide vane 

1. A compressor comprising: a casing that has a columnar shape and forms a space; a motor provided within the space of the casing with a clearance left between the casing and the motor; a rotation shaft that extends downstream from the motor, and is configured to output rotational driving force of the motor; an impeller fixed to the rotation shaft on a downstream side with respect to the motor, and configured to compress working fluid; and a first guide vane provided in the clearance, and configured to give a swirl component to working fluid that passes through the clearance and approaches the impeller in accordance with rotation of the impeller, wherein the casing includes a first drain hole opened to a portion between the impeller and the first guide vane in the space, liquid contained in the working fluid being discharged through the first drain hole.
 2. The compressor according to claim 1, wherein the casing includes an inlet port through which the working fluid enters the impeller, and an outside diameter of the motor is larger than an inlet diameter of the inlet port.
 3. The compressor according to claim 1, wherein the casing includes a second drain hole opened to the space and located on a downstream side with respect to the position of the first drain hole in a flow of the working fluid, liquid contained in the working fluid being discharged through the second drain hole.
 4. The compressor according to claim 3, wherein the casing includes an inlet port through which the working fluid enters the impeller, an outside diameter of the motor is larger than an inlet diameter of the inlet port, an inside diameter of a portion that is a part of the casing and houses the motor is larger than the inlet diameter of the inlet port, and the casing includes an inclined face that extends from the portion that houses the motor toward the inlet port while inclined toward the rotation shaft.
 5. The compressor according to claim 3, wherein each of the first drain hole and the second drain hole includes a liquid storage hole that stores liquid contained in the working fluid, and a drain port through which the liquid stored in the liquid storage hole goes out of the casing for discharge.
 6. The compressor according to claim 1, wherein a second guide vane configured to reduce a swirl component of the working fluid is provided at an inlet port portion that is a part of the casing and corresponds to an inlet through which the working fluid enters the impeller.
 7. The compressor according to claim 2, wherein the casing includes a second drain hole opened to the space and located on a downstream side with respect to the position of the first drain hole in a flow of the working fluid, liquid contained in the working fluid being discharged through the second drain hole.
 8. The compressor according to claim 2, wherein a second guide vane configured to reduce a swirl component of the working fluid is provided at an inlet port portion that is a part of the casing and corresponds to an inlet through which the working fluid enters the impeller.
 9. The compressor according to claim 3, wherein a second guide vane configured to reduce a swirl component of the working fluid is provided at an inlet port portion that is a part of the casing and corresponds to an inlet through which the working fluid enters the impeller.
 10. The compressor according to claim 4, wherein a second guide vane configured to reduce a swirl component of the working fluid is provided at an inlet port portion that is a part of the casing and corresponds to an inlet through which the working fluid enters the impeller.
 11. The compressor according to claim 5, wherein a second guide vane configured to reduce a swirl component of the working fluid is provided at an inlet port portion that is a part of the casing and corresponds to an inlet through which the working fluid enters the impeller. 